Method for making surface enhanced raman scattering device

ABSTRACT

A method for making a surface enhanced Raman scattering device in accordance with one aspect of the present invention comprises a first step of forming a nanoimprint layer on a main surface of a wafer including a plurality of portions each corresponding to a substrate; a second step of transferring, by using a mold having a pattern corresponding to a fine structural part, the pattern to the nanoimprint layer after the first step, and thereby forming the formed layer including the fine structural part for each portion corresponding to the substrate; a third step of forming a conductor layer on the fine structural part after the second step; and a fourth step of cutting the wafer into each portion corresponding to the substrate after the second step.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Provisional Application No.61/682,406 filed on Aug. 13, 2012, and Japanese Patent Application No.JP2012-178976 filed on Aug. 10, 2012, by the same applicant, which arehereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for making a surface enhancedRaman scattering device.

2. Related Background Art

As a conventional surface enhanced Raman scattering device, onecomprising a fine metal structural part which generates surface enhancedRaman scattering (SERS) has been known (see, for example, JapanesePatent Application Laid-Open No. 2011-33518 and “Q-SBRSTM G1 Substrate”,[online], Opto Science, Inc., [retrieved on 2012-07-19], retrieved fromthe Internet <URL:http/www.optoscience.com/maker/nanova/pdf/Q-SERS_G1.pdf>). In such asurface enhanced Raman scattering device, a sample subjected to Ramanspectrometry is brought into contact with the fine metal structuralpart. When the sample is irradiated with excitation light in this state,surface enhanced Raman scattering occurs, whereby Raman scattered lightenhanced by about 10⁸ times, for example, is emitted.

As a method for making a surface enhanced Raman scattering device suchas the one mentioned above, Japanese Patent Application Laid-Open No.2011-75348, for example, describes a method comprising forming aplurality of fine pillars on a substrate by vapor deposition and furtherforming metal films at top parts of the pillars by vapor deposition,thereby producing a fine metal structural part.

SUMMARY OF THE INVENTION

However, the above-mentioned surface enhanced Raman scattering devicemaking method forms a plurality of fine pillars on a substrate by vapordeposition and thus increases the time required for forming the pillars,while the pillars may have unstable forms.

It is therefore an object of the present invention to provide a surfaceenhanced Raman scattering device making method which can make a surfaceenhanced Raman scattering device efficiently and stably.

The surface enhanced Raman scattering device making method in accordancewith one aspect of the present invention is a method for making asurface enhanced Raman scattering device comprising a substrate having amain surface; a formed layer formed on the main surface and including afine structural part; and a conductor layer formed on the finestructural part and constituting an optical function part for generatingsurface enhanced Raman scattering; the method comprising a first step offorming a nanoimprint layer on a main surface of a wafer including aplurality of portions each corresponding to the substrate; a second stepof transferring, by using a mold having a pattern corresponding to thefine structural part, the pattern to the nanoimprint layer after thefirst step, and thereby forming the formed layer including the finestructural part for each portion corresponding to the substrate; a thirdstep of forming the conductor layer on the fine structural part afterthe second step; and a fourth step of cutting the wafer into eachportion corresponding to the substrate after the second step.

This surface enhanced Raman scattering device making method transfers apattern of a mold to a nanoimprint layer on a wafer, and thereby form aformed layer including a fine structural part for each portioncorresponding to a substrate. This can form the fine structural partefficiently and stably. Therefore, this surface enhanced Ramanscattering device making method can make a surface enhanced Ramanscattering device efficiently and stably.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, the fourth step maybe performed after the third step. This can form a conductor layercollectively for a plurality of fine structural parts on the wafer,whereby the surface enhanced Raman scattering device can be made moreefficiently.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, the mold may beflexible. This makes it easier to release the mold from the nanoimprintlayer. When a relatively large distortion or the like exists in thewafer in this case, the mold follows the distortion or the like in thewafer, whereby the fine structural part can be formed stably.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, the mold may beelastic. In this case, foreign matters and the like, if any, interveningbetween the mold and the nanoimprint layer are likely to bite onto themold. Therefore, areas of transfer failures can be suppressed. This canalso make it easier for the pattern of the mold to follow thenanoimprint layer, and thereby form the fine structural part stably.Further, when relatively small roughness and the like exist in the waferin this case, the mold follows the roughness and the like of the wafer,whereby the fine structural part can be formed more stably.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, the mold may have aplurality of patterns, and in the second step, a plurality of thepatterns may be simultaneously transferred to the nanoimprint layer byusing the mold. This can collectively form a plurality of finestructural parts for the nanoimprint layer on the wafer, whereby thesurface enhanced Raman scattering device can be made more efficiently.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, a plurality of thepatterns may be separated from each other, and in the second step, aplurality of the patterns may be simultaneously transferred to thenanoimprint layer by using the mold such that a plurality of finestructural parts are separated from each other. In this case, the wafercan be cut easily with reference to a space between adjacent finestructural parts as a guide for cutting.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, a plurality of thepatterns may be continuous, and in the second step, a plurality of thepatterns may be simultaneously transferred to the nanoimprint layer byusing the mold such that a plurality of fine structural parts arecontinuous. This can form a greater number of fine structural parts in asmall area than in the case where a plurality of fine structural partsare formed so as to be separated from each other, whereby a greaternumber of surface enhanced Raman scattering devices can be obtained fromthe wafer.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, in the fourth step,the formed layer and conductor layer existing on a line to cut passingbetween the portions corresponding to the substrates may be cut togetherwith the wafer. This can integrally form the formed layer and conductorlayer all over the portions corresponding to the substrates, whereby thesurface enhanced Raman scattering devices can be made more efficiently.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, in the fourth step,a fracture may be extended from a cutting start point formed in thewafer along the line and thereby the formed layer and conductor layerexisting on the line are cut together with the wafer. This makes itunnecessary for the formed layer and conductive layer to be formed witha cutting start point and thus can inhibit the fine structural part andoptical function part from being damaged.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, the formed layermay include a support for supporting the fine structural part on themain surface of the substrate and a ring-shaped frame surrounding thesupport on the main surface of the substrate, and in the fourth step, afracture may be extended from a cutting start point formed in the waferalong a line to cut passing between the portions corresponding to thesubstrates, and thereby the frame and conductor layer existing on theline are cut together with the wafer. In this case, the frame canfavorably buffer shocks caused by cutting and the like, whereby the finestructural part and optical function part can be inhibited from beingdamaged at the time of cutting.

In the surface enhanced Raman scattering device making method inaccordance with one aspect of the present invention, in the fourth step,the wafer may be irradiated with laser light while locating a convergingpoint within the wafer, and thereby a modified region is formed as thecutting start point within the wafer along the line. In this case, thewafer is hardly affected by the irradiation with the laser light exceptfor the vicinity of the converging point of the laser light therewithin,whereby the fine structural part and optical function part can beinhibited from being damaged at the time of cutting. Utilizing afracture having extended from the modified region, the formed layer andconductor layer on the line can accurately be cut together with thewater.

The present invention can provide a surface enhanced Raman scatteringdevice making method which can make a surface enhanced Raman scatteringdevice efficiently and stably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a surface enhanced Raman scattering unitcomprising the surface enhanced Raman scattering device in accordancewith one embodiment;

FIG. 2 is a sectional view taken along the line I-II of FIG. 1;

FIG. 3 is an enlarged sectional view of an optical function part in FIG.2;

FIG. 4 is a SEM photograph of the optical function part in FIG. 2;

FIG. 5 is a perspective view illustrating steps of making the surfaceenhanced Raman scattering device of FIG. 1;

FIG. 6 is a perspective view illustrating steps of making the surfaceenhanced Raman scattering device of FIG. 1;

FIG. 7 is a sectional view illustrating a step of cutting a wafer;

FIG. 8 is a perspective view illustrating a step of cutting the wafer;

FIG. 9 is a perspective view illustrating a step of making the surfaceenhanced Raman scattering device in accordance with another embodiment;

FIG. 10 is an enlarged sectional view illustrating a modified example ofFIG. 3;

FIG. 11 is a sectional view illustrating a modified example of the stepof cutting the wafer;

FIG. 12 is a sectional view illustrating the modified example of thestep of cutting the wafer; and

FIG. 13 is a sectional view illustrating the modified example of thestep of cutting the wafer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments will be explained in detail with referenceto the drawings. In the drawings, the same or equivalent parts will bereferred to with the same signs while omitting their overlappingexplanations.

As illustrated in FIGS. 1 and 2, a SERS unit (surface enhanced Ramanscattering unit) 1 comprises a handling substrate 2 and a SERS device(surface enhanced Raman scattering device) 3 attached onto the handlingsubstrate 2. The handling substrate 2 is a rectangular sheet-like glassslide, resin substrate, ceramic substrate, or the like. The SERS device3 is arranged on a front face 2 a of the handling substrate 2 whilebeing lopsided to one longitudinal end part of the handling substrate 2.

The SERS device 3 comprises a substrate 4 attached onto the handlingsubstrate 2, a formed layer 5 formed on the substrate 4, and a conductorlayer 6 formed on the formed layer 5. The substrate 4 is formed fromsilicon, glass, or the like into a rectangular sheet having an outershape on the order of several 100 μm×several 100 μm to several 10mm×several 10 mm with a thickness on the order of 100 μm to 2 mm. Thesubstrate 4 has a rear face 4 b secured to the front face 2 a of thehandling substrate 2 by direct bonding, bonding with a metal such assolder, eutectic bonding, fusion bonding by irradiation with laser lightor the like, anodic bonding, or bonding with a resin.

As illustrated in FIG. 3, the formed layer 5 includes a fine structuralpart 7, a support 8, and a frame 9. The fine structural part 7, which isa region having a periodic pattern, is formed on a surface on the sideopposite from the substrate 4 at a center part of the formed layer 5. Inthe fine structural part 7, a plurality of cylindrical pillars 71 havinga diameter and height in the order of several nm to several μm areperiodically arranged with a pitch on the order of several 10 nm toseveral 100 nm along a front face (main surface) 4 a of the substrate 4.The fine structural part 7 has a rectangular outer shape on the order ofseveral 100 μm×several 100 μm to several 10 mm×several 10 mm when seenin the thickness direction of the substrate 4. The support 8, which is arectangular region for supporting the fine structural part 7, is formedon the front face 4 a of the substrate 4. The frame 9, which is arectangular-ring-shaped region surrounding the fine structural part 7and support 8, is formed on the front face 4 a of the substrate 4. Eachof the support 8 and frame 9 has a thickness on the order of several 10nm to several 10 μm.

The distance from the front face 8 a of the support 8 to the surface offrame 9 opposite from the substrate 4 (i.e., the height of the frame 9)is greater than the height of the fine structural part 7. The height ofthe frame 9 may also be substantially the same as that of the finestructural part 7 as illustrated in FIG. 10. The area of the contactsurface between a replica mold R (which will be explained later) and theframe 9 at an end part of the fine structural part 7 is smaller (or, inother words, the surface energy becomes smaller) when the height of theframe 9 is substantially the same as that of the fine structural part 7than when the height of the frame 9 is greater than that of the finestructural part 7. This makes it possible to inhibit both structures ofthe replica mold R and frame 9 at the end part of the fine structuralpart 7 from being damaged when releasing the replica mold R from theformed layer 5. The amount of the nanoimprint resin used in the formedlayer 5 can also be made smaller. The height of the frame 9 may be madelower than that of the fine structural part 7, which also seems to yieldthe above-mentioned effects at the time of molding. From the viewpointof protecting the fine structural part 7, however, it is desirable forthe frame 9 to have a height not lower than that of the fine structuralpart 7. Hence, the above-mentioned effect at the time of forming and theprotection of the fine structural part 7 can be satisfied at the sametime when the frame 9 and fine structural part 7 have substantially thesame height as illustrated in FIG. 10.

The formed layer 5 is integrally formed by molding a resin (examples ofwhich include acrylic, epoxy, silicone, and urethane resins, PET,polycarbonates, and inorganic-organic hybrid materials) or low-meltingglass arranged on the substrate 4 by nanoimprinting, for example.

The conductor layer 6 is formed so as to extend over the fine structuralpart 7 and frame 9. In the fine structural part 7, the conductor layer 6is formed on the surfaces of the pillars 71 and the front face 8 a ofthe support 8 exposed on the side opposite from the substrate 4. Theconductor layer 6 has a thickness on the order of several nm to severalμm. The conductor layer 6 is formed by vapor-depositing a conductor suchas a metal (examples of which include Au, Ag, Al, Cu, and Pt) on theformed layer 5 molded by nanoimprinting, for example. In the SERS device3, an optical function part 10 which generates surface enhanced Ramanscattering is constructed by the conductor layer 6 formed on thesurfaces of the pillars 71 and the surface 8 a of the support 8.

FIG. 4 is a SEM photograph of the optical function part in FIG. 2. Theoptical function part illustrated in FIG. 4 is one in which Au isvapor-deposited as a conductor layer with a thickness of 50 nm on a finestructural part made of a nanoimprint resin having a plurality ofpillars (each having a diameter of 120 nm and a height of 180 nm)periodically arranged at a predetermined pitch (a distance of 360 nmbetween center lines).

Thus constructed SERS unit 1 is used as follows. First, the SERS unit 1is prepared. Subsequently, using a pipette or the like, a solutionsample (or a dispersion of a powder sample in a solution such as wateror ethanol, as the case may be) is applied dropwise to a depression Cdefined by the support 8 and frame 9 of the formed layer 5, so that thesample is arranged on the optical function part 10. Subsequently, inorder to reduce the lens effect, cover glass is mounted on the frame 9,and thereby come into close contact with the solution sample.

Next, the SERS unit 1 is set in a Raman spectrometer, and the samplearranged on the optical function part 10 is irradiated with excitationlight through the cover glass. This generates surface enhanced Ramanscattering at the interface between the optical function part 10 and thesample, whereby Raman scattered light derived from the sample isenhanced by about 10⁸ times, for example, and then emitted. Hence,highly sensitive and highly accurate Raman spectrometry is possible inthe Raman spectrometer.

Not only the above-mentioned method, but the following methods may alsobe used for arranging the sample onto the optical function part 10. Forexample, the handling substrate 2 may be nipped so that the SERS device3 is dipped into a solution sample (or a dispersion of a powder samplein a solution such as water or ethanol), lifted up therefrom, and thenblown to dry. A minute amount of a solution sample (or a dispersion of apowder sample in a solution such as water or ethanol) may be applieddropwise onto the optical function part 10 aid left to dry naturally. Apowder sample may be dispersed as it is on the optical function part 10.Note that mounting of the cover glass is not indispensable at the timethe measurement is conducted in these methods.

A method for making the SERS device 3 will now be explained. First, asillustrated in (a) of FIG. 5, a master mold M1 and a film base F areprepared. The master mold M1 has a plurality of patterns MP arranged ina matrix. Each pattern MP includes a fine structural part M7corresponding to the fine structural part 7 and a support M8 supportingthe fine structural part M7. In the master mold M1, the plurality ofpatterns MP are separated from each other by a frame M9 corresponding tothe frame 9. Note that master mold M1 may be surface treated such as byapplying mold lubricants or the like so as to enable easy demoldingduring a latter process.

Next, the film base F is pressed against the master mold M1 andpressurized and heated in this state, and thereby the patterns MP of themaster mold M1 are transferred to the film base F (thermal nanoimprint).Subsequently, the film base F is released from the master mold M1, andthereby a replica mold (replica film) R having a plurality of patternsRP in the reverse of the patterns MP of the master mold M1 is yielded asillustrated in (b) of FIG. 5. In the replica mold R, the plurality ofpatterns RP are separated from each other. Here, the replica mold R iselastic and flexible. Its elasticity and flexibility derive from thematerial (examples of which include PET (polyethylene terephthalate),polycarbonate, silicone, polyimide, and fluorine resins) and thicknessof the film base F, for example. This makes the replica mold R moreelastic and flexible than molds formed from hard materials such assilica, silicon, and nickel. The replica mold R is also more elastic andflexible than a wafer 40 (which will be explained later). Repeating theforegoing process can yield a plurality of replica molds R. The replicamold R may also be formed by applying a resin (examples of which includeepoxy, acrylic, fluorine, silicone, urethane, and inorganic-organichybrid resins) onto the film base F. When the resin applied onto thefilm base is UV-curable, it may be cured by irradiation with UV insteadof thermal nanoimprint, and thereby the replica mold R is yielded (UVnanoimprint). Note that replica mold R may be surface treated such as byapplying mold lubricants or the like so as to enable easy demoldingduring a latter process.

Then, as illustrated in (c) of FIG. 5, the wafer 40 including aplurality of portions corresponding to the substrates 4 is prepared, anda UV-curable resin is applied to its front face 40 a, and thereby ananoimprint layer 50 to become the formed layer 5 is formed on the wafer40.

Thereafter, the replica mold R is pressed against the nanoimprint layer50 on the wafer 40, and the nanoimprint layer 50 is cured by irradiationwith UV in this state, whereby a plurality of patterns RP in the replicamold R are transferred simultaneously to the nanoimprint layer 50.Subsequently, the replica mold R is released from the nanoimprint layer50. This forms the formed layer 5 having fine structural parts 7 atrespective portions corresponding to the substrates 4 on the wafer 40. Aplurality of fine structural parts 7 are formed so as to be separatedfrom each other by the frames 9, while the frames 9 adjacent to eachother are formed so as to be continuous. Repeating the foregoing processcan yield a plurality of wafers 40 each having the main surface 40 a onwhich a plurality of fine structural parts 7 are formed.

Next, as illustrated in (a1) of FIG. 6, a film of a metal such as Au orAg is formed on the formed layer 5 by vapor deposition, such asresistance heating vapor deposition or electron beam vapor deposition,or sputtering, and thereby the conductor layer 6 is formed. This formsoptical function parts 10 at respective portions corresponding to thesubstrates 4 on the wafer 40. On the wafer 40, the plurality of opticalfunction parts 10 are formed so as to be separated from each other,while the conductor layer 6 is formed continuously over the frames 9adjacent to each other. Subsequently, as illustrated in (b1) of FIG. 6,the wafer 40, formed layers 5, and conductor layer 6 are cut into theindividual portions corresponding to the substrates 4, and thereby aplurality of SERS devices 3 are yielded. More specifically, lines to cutare set like grids so as to pass between the portions corresponding tothe substrates 4, and the wafer 40 is cut along the lines, while theframes 9 of the formed layers 5 and conductor layer 6 existing on thelines are cut. Then, as illustrated in (c) of FIG. 6, the cut SERSdevice 3 is secured to (mounted on) the handling substrate 2, andthereby the SERS unit 1 is yielded, which is packed thereafter.

Here, the wafer 40 and formed layers 5 may be cut into chips forrespective portions corresponding to the substrates 4 as illustrated in(a2) of FIG. 6, the conductor layer 6 may be formed on the finestructural part 7 of each chip as illustrated in (b2) of FIG. 6, andthen mounting and packing may be performed as illustrated in (c) of FIG.6. This can inhibit the conductor layer 6 including the optical functionpart 10 from being contaminated, since the conductor layer 6 is formedafter cutting the wafer 40 and formed layers 5.

The above-mentioned cutting of the wafer 40 is performed as in thefollowing, for example. The case of cutting the formed layers 5 andconductor layer 6 together with the wafer 40 (the case of (a1) and (b1)in FIG. 6) will be explained here.

First, as illustrated in FIG. 7, a tape B such as a light-transmittingexpandable tape is attached to the rear face 40 b of the wafer 40.Subsequently, the wafer 40 is irradiated with laser light L through thetape B while locating a converging point P within the wafer 40, andthereby modified regions RA are formed within the wafer 40 along linesto cut CL.

Next, as illustrated in FIG. 8, a tensile load TF is applied to the tapeE, so that fractures extend in the thickness direction of the wafer 40from the modified regions RA, thereby cutting the frames 9 of the formedlayers 5 and conductor layer 6 existing on the lines CL together withthe wafer 40.

For cutting the frames 9 of the formed layers 5 and conductor layer 6existing on the lines CL by utilizing the extension of fractures underthe tensile load, it is preferred for the frame 9 and conductor layer 6to have thicknesses of 50 μm or less and 2 μm or less, respectively. Inthis case, the frames 9 of the formed layers 5 and conductor layer 6existing on the lines CL can be cut accurately along the lines CL.

As in the foregoing, the method for making the SERS device 3 transfersthe patterns RP of the replica mold R to the nanoimprint layer 50 on thewafer 40, and thereby the formed layers 5 including the fine structuralparts 7 are formed for the respective portions corresponding to thesubstrates 4. This can form the fine structural parts 7 efficiently andstably. Therefore, this method for making the SERS device 3 can make theSERS device 3 efficiently and stably.

In the above-mentioned method for making the SERS device 3, the step ofcutting the wafer 40 into the respective portions corresponding to thesubstrates 4 is performed after the step of forming the conductor layer6 on the fine structural parts 7. Therefore, the conductor layer 6 canbe formed collectively for a plurality of fine structural parts 7 on thewafer 40, whereby the SERS device 3 can be made more efficiently.

In the above-mentioned method for making the SERS device 3, the replicamold R is flexible. This makes it easier to release the mold from thenanoimprint layer. The effect of making the mold easier to release ismore favorably exhibited in the method of this embodiment, since thereplica mold R having a plurality of patterns RP is used in order toform a plurality of formed layers 5 at the same time. When a hard moldis used, the mold and wafer 40 must be torn apart from each other indirections vertically opposite from each other, since the wafer 40,which is formed from silicon, glass, or the like, is also hard. In thiscase, the surface energy is so high that care must be taken for thepeeling of the formed layers 5, damages to the mold and substrates 4,and the like. The flexible replica mold R, on the other hand, can betorn away from an end part with a small energy, which makes it easier torelease, while inhibiting the formed layers 5 from peeling, the mold andsubstrates 4 from being damaged, and so forth.

In the above-mentioned method for making the SERS device 3, the replicamold R is flexible and thus follows relatively large distortions and thelike, if any, of the wafer 40, whereby the fine structural parts 7 canbe formed stably.

In the above-mentioned method for making the SERS device 3, the replicamold R is elastic. Here, when a hard mold is used, foreign matters andthe like, if any, intervening between the replica mold R and thenanoimprint layer 50 may bite onto the nanoimprint layer 50, while apert of the nanoimprint layer 50 pushed back by the biting of theforeign matters may project so as to surround the foreign matters andthe like. When a hard mold is used, a region to which the patterns RPare not transferred may occur in the nanoimprint layer 50 in thevicinity of the area where the foreign matters bite. When a hard mold isused, as the pressure is increased, foreign matters and the like maycrush, thereby expanding defect regions such as those incurringprojections and those having no patterns RP transferred thereto asmentioned above. When the elastic mold is used, on the other hand,foreign matters are likely to bite onto the mold, so that defect regionscan be suppressed to a size on a par with that of the foreign mattersand the like. This can suppress areas of transfer failures.

In the above-mentioned method for making the SERS device 3, the replicamold R is elastic, so that its patterns are easier to follow thenanoimprint layer 50. Hence, the fine structural parts 7 can be formedmore stably.

In the above-mentioned method for making the SERS device 3, the replicamold R is elastic and thus follows relatively small roughness, if any,existing in the wafer 40, whereby the fine structural parts 7 can beformed more stably.

In the above-mentioned method for making the SERS device 3, the replicamold R has a plurality of patterns RP, and in the step of forming theformed layers 5 including the fine structural parts 7, the plurality ofpatterns RP are simultaneously transferred to the nanoimprint layer 50by using the replica mold R. This makes it possible to form a pluralityof fine structural parts 7 collectively for the nanoimprint layer 50 onthe wafer 40, whereby the SERS device 3 can be made more efficiently.

When forming a plurality of formed layers 5 by so-called stepping andrepeating, it is required to set a long distance between the patterns RPadjacent to each other in view of the case where the nanoimprint layer50 protrudes out of its desirable area. In contrast, the above-mentionedmethod for making the SERS device 3 forms a plurality of formed layers 5at the same time by using the replica mold R having a plurality ofpatterns RP and thus can arrange a greater number of patterns RP on thewafer 40 than when forming a plurality of formed layers 5 sequentially,whereby the SERS device 3 can be made more efficiently.

When forming the formed layers 5 by stepping and repeating, a pluralityof formed layers 5 are formed sequentially for one wafer 40, which takesa very long time. Attention must also be paid to the fact that, during aplurality of molding operations, a part of the nanoimprint layer 50 mayadhere to the replica mold R and transfer to the subsequently moldedproduct, thereby lowering the yield. In contrast, the above-mentionedmethod for making the SERS device 3 forms a plurality of formed layers 5at the same time and thus can attain high productivity and high yield.

In the above-mentioned method for making the SERS device 3, theplurality of patterns RP are separated from each other in the replicamold R, and in the step of forming the formed layers 5 including thefine structural parts 7, a plurality of patterns RP are simultaneouslytransferred to the nanoimprint layer 50 by using the replica mold R suchthat the plurality of fine structural parts 7 are separated from eachother. Hence, the wafer 40 can be cut easily with reference to a spacebetween the adjacent fine structural parts 7, 7 as a guide for cutting.

The above-mentioned method for making the SERS device 3 forms aplurality of fine structural parts 7 such that they are separated fromeach other. Hence, the method of this embodiment can vary the pitch ofpillars 71 among a plurality of fine structural parts 7, for example.

When the pitch of the pillars 71 is set shorter in the case of formingthe replica mold R by thermal nanoimprint or UV nanoimprint as mentionedabove, the replica mold R is constructed relatively thin in its centerpart contributing to forming the fine structural parts 7 but relativelythick in its outer edge part. The SERS device 3 formed by this replicamold R is constructed relatively thick in its center part formed withthe fine structural part 7 but relatively thin in its outer edge part.The SERS device 3 having the relatively thick center part is easier tokeep the form of the fine structural part 7 at the center part whenreleasing the replica mold R from the formed layer 5. Hence, the SERSdevice 3 having the relatively thick center part has a characteristic ofbeing able to inhibit the fine structural part 7 from being damaged.

When the pitch of the pillars 71 is set longer in the case of formingthe replica mold R by thermal nanoimprint or UV nanoimprint, on theother hand, the replica mold R is constructed relatively thick in itscenter part contributing to forming the fine structural parts 7 butrelatively thin in its outer edge part. The SERS device 3 formed by thisreplica mold R is constructed relatively thin in its center part formedwith the fine structural part 7 but relatively thick in its outer edgepart. The SERS device 3 having the relatively thin center part reducesthe amount of deformation caused by shrinkage on curing or thermalexpansion in the center part formed with the fine structural part 7.Furthermore, the SERS device 3 having the relatively thick outer edgepart mitigates distortions caused by the difference in coefficient ofthermal expansion with respect to the substrate 4. Hence, the SERSdevice 3 having the relatively thin center part has a characteristic ofbeing able to stabilize the property of surface enhanced Ramanscattering.

The above-mentioned method for making the SERS device 3 can vary thepitch of pillars 71 among a plurality of fine structural parts 7 andthus can simultaneously mold a plurality of SERS devices 3 havingrespective thickness distribution structures different from each other.Hence, the method of this embodiment can simultaneously form a pluralityof SERS devices 3 for which respective characteristics different fromeach other are demanded.

In the above-mentioned method for making the SERS device 3, in the stepof cutting the wafer 40 into the respective portions corresponding tothe substrates 4, the formed layers 5 and conductor layer 6 existing onthe lines CL passing between the portions corresponding to thesubstrates 4 are cut together with the wafer 40. This can integrallyform the formed layers 5 and conductor layer 6 all over the portionscorresponding to the substrates 4, whereby the SERS device 3 can be mademore efficiently. Since the conductor layer 6 exists over the lines CLfor cutting the wafer 40, the fine structural parts 7 can be arrangedefficiently. This also makes it possible to omit the step for formingdicing lines in the formed layers 5 and conductor layer 6.

In the above-mentioned method for making the SERS device 3, in the stepof cutting the wafer 40 into the respective portions corresponding tothe substrates 4, fractures are extended from the modified regions RAformed in the wafer 40 along the lines CL, thereby cutting the formedlayers 5 and conductor layer 6 existing on the lines CL together withthe wafer 40. This makes it unnecessary to form the formed layers 5 andconductor layer 6 with cutting start points, whereby the fine structuralparts 7 and optical function parts 10 can be inhibited from beingdamaged.

When cutting the formed layers 5 and conductor layer 6 by laser, forexample, materials forming the formed layers 5 and conductor layer 6 mayalter (e.g., change structures as being melted by heat and carbonize).When cutting the formed layers 5 and conductor layer 6 by blade dicing,for example, cutting blades, cutting agents (e.g., water, oils, andgases), and the like may contaminate the materials forming the formedlayers 5 and conductor layer 6. In contrast, the above-mentioned methodfor making the SERS device 3 can prevent the materials of the formedlayers 5 and conductor layer 6 from being altered, contaminated, and soforth.

In the above-mentioned method for making the SERS device 3, the formedlayer 5 includes the support 8 for supporting the fine structural part 7on the main surface 4 a and the ring-shaped frame 9 for surrounding thesupport 8 on the main surface 4 a, and in the step of cutting the wafer40 into the respective portions corresponding to the substrate 4,fractures are extended from the modified regions RA formed in the wafer40 along the lines CL passing between the portions corresponding to thesubstrates 4, thereby cutting the frames 9 and conductor layer 6existing on the lines CL together with the wafer 40. Hence, the frames 9can favorably buffer shocks caused by cutting and the like, whereby thefine structural part 7 and optical function part 10 can be inhibitedfrom being damaged at the time of cutting.

In the above-mentioned method for making the SERS device 3, in the stepof cutting the wafer 40 into the respective portions corresponding tothe substrate 4, the wafer 40 is irradiated with the laser light L whilelocating the converging point P within the wafer 40, and thereby themodified regions RA are formed as cutting start points within the wafer40 along the lines CL. Hence, the wafer 40 is hardly affected by theirradiation with the laser light L except for the vicinity of theconverging point P of the laser light L therewithin, whereby the finestructural part 7 and optical function part 10 can be inhibited frombeing damaged at the time of cutting. Utilizing fractures havingextended from the modified regions RA, the formed layers 5 and conductorlayer 6 on the lines CL can accurately be cut together with the wafer40.

When cutting the wafer 40 by blade dicing, for example, a protectivefilm or the like for protecting the fine structural parts 7 isnecessary. In contrast, the above-mentioned method for making the SERSdevice 3 can save the step of providing the protective film or the like.When providing the protective film or the like, care must be taken tokeep the protective film from contaminating the fine structural parts 7.Such care is unnecessary in the above-mentioned method for making theSERS device 3.

When cutting the wafer 40 by blade dicing, for example, the formedlayers 5 may peel from the substrate 4. In contrast, the above-mentionedmethod for making the SERS device 3 cuts the frames 9 and conductorlayer 6 by a tensile load. Hence, the above-mentioned method for makingthe SERS device 3 can inhibit the formed layers 5 from peeling from thesubstrates 4.

A method for making a SERS unit in accordance with another embodimentwill now be explained.

FIG. 9 is a schematic view for explaining the method in accordance withanother embodiment. This embodiment forms a plurality of fine structuralparts 7 continuously in a nanoimprint layer 50 at the time ofnanoimprinting.

In this embodiment, a pattern MP of a master mold M2 includes a finestructural part M7 corresponding to the fine structural part 7 of theformed layer 5 and a support M8 supporting the fine structural part M7.The master mold M2 does not include the frames M9 (see (a) of FIG. 5)corresponding to the frames 9 of the formed layers 5. In the master moldM2, a plurality of patterns MP are continuous.

The method of this embodiment using the master mold M2 transfers thepatterns MP of the master mold M2 to a film base P by thermalnanoimprint or UV nanoimprint. Subsequently, the film base F is releasedfrom the master mold M2. This yields a replica mold R having a pluralityof patterns RP in the reverse of the patterns MP of the master mold M2.In the replica mold R, the plurality of patterns RP are continuous.

Then, a wafer 40 including a plurality of portions corresponding tosubstrates 4 is prepared, and a nanoimprint resin is arranged over theplurality of portions corresponding to the substrates 4 on its frontface (main surface) 40 a, and thereby a nanoimprint layer 50 is formedintegrally.

Next, the plurality of patterns RP in the replica mold R are transferredsimultaneously to the nanoimprint layer 50 by nanoimprint. Here, aplurality of fine structural parts 7 are formed so as to be continuous.Performing the remaining steps as mentioned above can yield the SERSdevice 3 having pillars 71 formed close to outer edge parts of theformed layers 5.

As in the foregoing, in the method for making the SERS device 3, thepatterns RP of the replica mold R are transferred to the nanoimprintlayer 50 on the wafer 40, and thereby the formed layers 5 including thefine structural parts 7 are formed for the respective portionscorresponding to the substrates 4. This can form the fine structuralparts 7 efficiently and stably. Therefore, this method for making theSERS device 3 can make the SERS device 3 efficiently and stably.

In the above-mentioned method for making the SERS device 3, the step ofcutting the wafer 40 into the respective portions corresponding to thesubstrates 4 is performed after the step of forming the conductor layer6 on the fine structural parts 7. Therefore, the conductor layer 6 canbe formed collectively for a plurality of fine structural parts 7 on thewafer 40, whereby the SERS device 3 can be made more efficiently.

In the above-mentioned method for making the SERS device 3, the replicamold R is flexible. This makes it easier to release the mold from thenanoimprint layer, while inhibiting the formed layers 5 from peeling themold and substrates 4 from being damaged, and so forth. In particular,the method of this embodiment uses the replica mold R having a pluralityof patterns RP in order to form a plurality of formed layers 5 at thesame time and thus more favorably exhibits the effects mentioned above.

In the above-mentioned method for making the SERS device 3, the replicamold R is flexible and thus follows relatively large distortions and thelike, if any, of the wafer 40, whereby the fine structural parts 7 canbe formed stably.

In the above-mentioned method for making the SERS device 3, the replicamold R is elastic. Therefore, foreign matters and the like, if any,intervening between the replica mold R and the nanoimprint layer 50 arelikely to bite onto the mold R, so that defect regions can be suppressedto a size on a par with that of the foreign matters and the like. Thiscan suppress areas of transfer failures.

In the above-mentioned method for making the SERS device 3, the replicamold R is elastic, so that its patterns are easier to follow thenanoimprint layer 50. Hence, the fine structural parts 7 can be formedmore stably.

In the above-mentioned method for making the SERS device 3, the replicamold R is elastic and thus follows relatively small roughness, if any,existing in the wafer 40, whereby the fine structural parts 7 can beformed more stably.

In the above-mentioned method for making the SERS device 3, the replicamold R has a plurality of patterns RP, and in the step of forming theformed layers 5 including the fine structural parts 7, the plurality ofpatterns RP are simultaneously transferred to the nanoimprint layer 50by using the replica mold R. This makes it possible to form a pluralityof fine structural parts 7 collectively for the nanoimprint layer 50 onthe wafer 40, whereby the SERS device 3 can be made more efficiently.This can also inhibit the nanoimprint layer 50 from protruding out ascompared with the case of forming a plurality of formed layers 5sequentially by so-called stepping and repeating, so that a greaternumber of patterns RP can be arranged on the wafer 40, whereby the SERSdevice 3 can be made more efficiently.

In the above-mentioned method for making the SERS device 3, a pluralityof patterns RP are continuous in the replica mold R, and in the step offorming the formed layers 5 including the fine structural parts 7, aplurality of patterns are simultaneously transferred to the nanoimprintlayer 50 by using the replica mold R such that the plurality of finestructural parts 7 are continuous. This can form a greater number offine structural parts 7 in a small area than in the case where they areformed so as to be separated from each other.

In the above-mentioned method for making the SERS device 3, in the stepof cutting the wafer 40 into the respective portions corresponding tothe substrates 4, the formed layers 5 and conductor layer 6 existing onthe lines CL passing between the portions corresponding to thesubstrates 4 are cut together with the wafer 40. This can integrallyform the formed layers 5 and conductor layer 6 all over the portionscorresponding to the substrates 4, whereby the SERS device 3 can be mademore efficiently. Since the conductor layer 6 exists over the lines CLfor cutting the wafer 40, the fine structural parts 7 can be arrangedefficiently. This also makes it possible to save the step for formingdicing lines in the formed layers 5 and conductor layer 6.

In the above-mentioned method for making the SERS device 3, in the stepof cutting the wafer 40 into the respective portions corresponding tothe substrates 4, fractures are extended from the modified regions RAformed in the wafer 40 along the lines CL, thereby cutting the formedlayers 5 and conductor layer 6 existing on the lines CL together withthe wafer 40. This makes it unnecessary to form the formed layers 5 andconductor layer 6 with cutting start points, whereby the fine structuralparts 7 and optical function parts 10 can be inhibited from beingdamaged. This can also prevent materials of the formed layers 5 andconductor layer 6 from being altered, contaminated, and so forth.

In the above-mentioned method for making the SERS device 3, in the stepof cutting the wafer 40 into the respective portions corresponding tothe substrate 4, the wafer 40 is irradiated with the laser light L whilelocating the converging point P within the wafer 40, and thereby themodified regions RA are formed as cutting start points within the wafer40 along the lines CL. Hence, the wafer 40 is hardly affected by theirradiation with the laser light L except for the vicinity of theconverging point P of the laser light L therewithin, whereby the finestructural part 7 and optical function part 10 can be inhibited frombeing damaged at the time of cutting. Utilizing fractures havingextended from the modified regions RA, the formed layers 5 and conductorlayer 6 on the lines CL can accurately be cut together with the wafer40. This can save the step of providing a protective film or the likeand prevent the protective film or the like from contaminating the finestructural parts 7. This can also inhibit the formed layers 5 frompeeling from the substrates 4.

The present invention is not limited to the embodiments explained in theforegoing. For example, the cross-sectional forms of the pillars 71 arenot necessarily circular, but may also be elliptical or polygonal, e.g.,triangular or quadrangular. Thus, various materials and forms can beemployed for each structure of the SERS device 3 without beingrestricted to those mentioned above. Furthermore, the arrangement of thepillars 71 is not limited to a matrix, but it may be a staggeredarrangement, a triangular grid arrangement, a random arrangement, or thelike.

The conductor layer 6 may be formed on the fine structural parts 7either directly or indirectly through any layers such as layers ofbuffer metals (e.g., Ti and Cr) for improving the adhesion of metals tothe fine structural parts 7.

The frame 9 may surround the support 8 alone instead of the support 8and fine structural part 7.

In the nanoimprint step illustrated in (a) to (c) of FIG. 5, a pluralityof formed layers may be formed sequentially by repeatedly using areplica mold having a size smaller than that of the wafer 40 (steppingand repeating) as mentioned above.

When cutting the wafer 40 by extending fractures from the modifiedregions RA, the modified regions RA may be formed before making theconductor layer 6. FIGS. 11 to 13 are sectional views illustrating amodified example of the step of cutting the wafer.

First, as illustrated in FIG. 11, the tape B is attached to the rearface 40 b of the wafer 40 before making the conductor layer 6 afterforming the formed layers 5. Subsequently, the wafer 40 is irradiatedwith the laser light L through the formed layers 5 from the front face40 a side while locating the converging point P within the wafer 40, andthereby the modified regions RA is formed within the wafer 40 along thelines CL. In this example, the tape E is not required to be transparentto light. The tape E may be attached to the rear face 40 b of the wafer40 after forming the conductor layer 6, which will be explained later.The type of the tape B may be changed according to the stage of formingthe modified regions RA in FIG. 11 and respective stages of forming theconductor layer 6 in FIG. 12 and cutting the wafer 40 in FIG. 13, whichwill be explained later.

Next, as illustrated in FIG. 12, a film of a metal such as Au or Ag isformed on the formed layers 5, and thereby the conductor layer 6 ismade. This forms the optical function parts 10 at respective portionscorresponding to the substrates 4 on the wafer 40.

Subsequently, while the tensile load TF is applied to the tape E, acutting assisting unit U having irregularities (e.g., saw-likeirregularities) is struck on the rear face 40 b of the wafer 40 throughthe tape B, so as to extend fractures in the thickness direction of thewafer 40 from the modified regions RA formed within the wafer 40,thereby cutting the frames 9 of the formed layers 5 and conductor layer6 existing on the lines CL together with the wafer 40. This yields aplurality of SERS devices 3. Then, thus cut SERS device 3 is secured(mounted) to the handling substrate 2, and thereby the SERS unit 1 isyielded, which is packed thereafter.

In this example, the wafer 40 is irradiated with the laser light L fromthe front face 40 a side, which makes it unnecessary for the tape B tobe transparent to light. This can widen the range of selectable types ofthe tape E.

The step of cutting the wafer 40 into the respective portionscorresponding to the substrates 40 is performed after the step offorming the conductor layer 6 on the fine structural parts 7, so thatthe conductor layer 6 can be formed collectively for a plurality of finestructural parts 7 on the wafer 40, whereby the SERS device 3 can bemanufactured more efficiently.

The modified regions RA are formed before making the conductor layer 6;after forming the conductor layer 6, the wafer 40 is cut by extendingfractures from the modified regions RA, and then mounted and packed,whereby the time elapsing before mounting and packing after forming theconductor layer 6 can be made shorter, and thereby the conductor layer 6including the optical function parts 10 is inhibited from beingcontaminated.

REFERENCE SIGNS LIST

-   -   3 . . . SERS device (surface enhanced Raman scattering device);        4 . . . substrate; 4 a . . . front face (main surface); 5 . . .        formed layer; 6 . . . conductor layer; 7 . . . fine structural        part; 8 . . . support; 9 . . . frame; 10 . . . optical function        part; 40 . . . wafer; 40 a . . . front face (main surface); 50 .        . . nanoimprint layer, R . . . replica mold; RA . . . modified        region; RP . . . pattern

What is claimed is:
 1. A method for making a surface enhanced Ramanscattering device comprising a substrate having a main surface; a formedlayer formed on the main surface and including a fine structural part;and a conductor layer formed on the fine structural part andconstituting an optical function part for generating surface enhancedRaman scattering the method comprising: a first step of forming ananoimprint layer on a main surface of a wafer including a plurality ofportions each corresponding to the substrate; a second step oftransferring, by using a mold having a pattern corresponding to the finestructural part, the pattern to the nanoimprint layer after the firststep, and thereby forming the formed layer including the fine structuralpart for each portion corresponding to the substrate; a third step offorming the conductor layer on the fine structural part after the secondstep; and a fourth step of cutting the wafer into each portioncorresponding to the substrate after the second step.
 2. The method formaking a surface enhanced Raman scattering device according to claim 1,wherein the fourth step is performed after the third step.
 3. The methodfor making a surface enhanced Raman scattering device according to claim1, wherein the mold is flexible.
 4. The method for making a surfaceenhanced Raman scattering device according to claim 1, wherein the moldis elastic.
 5. The method for making a surface enhanced Raman scatteringdevice according to claim 1, wherein the mold has a plurality of suchpatterns; and wherein, in the second step, a plurality of the patternsare simultaneously transferred to the nanoimprint layer by using themold.
 6. The method for making a surface enhanced Raman scatteringdevice according to claim 5, wherein a plurality of the patterns areseparated from each other; and wherein, in the second step, a pluralityof the patterns are simultaneously transferred to the nanoimprint layerby using the mold such that a plurality of the fine structural parts areseparated from each other.
 7. The method for making a surface enhancedRaman scattering device according to claim 5, wherein a plurality of thepatterns are continuous; and wherein, in the second step, a plurality ofthe patterns are simultaneously transferred to the nanoimprint layer byusing the mold such that a plurality of the fine structural parts arecontinuous.
 8. The method for making a surface enhanced Raman scatteringdevice according to claim 1, wherein, in the fourth step, the formedlayer and conductor layer existing on a line to cut passing between theportions corresponding to the substrates are cut together with thewafer.
 9. The method for making a surface enhanced Raman scatteringdevice according to claim 8, wherein, in the fourth step, a fracture isextended from a cutting start point formed in the wafer along the lineand thereby the formed layer and conductor layer existing on the lineare cut together with the wafer.
 10. The method for making a surfaceenhanced Raman scattering device according to claim 6, wherein theformed layer includes a support for supporting the fine structural parton the main surface of the substrate and a ring-shaped frame surroundingthe support on the main surface of the substrate; and wherein, in thefourth step, a fracture is extended from a cutting start point formed inthe wafer along a line to cut passing between the portions correspondingto the substrates, and thereby the frame and conductor layer existing onthe line are cut together with the wafer.
 11. The method for making asurface enhanced Raman scattering device according to claim 9, wherein,in the fourth step, the wafer is irradiated with laser light whilelocating a converging point within the wafer, and thereby a modifiedregion is formed as the cutting start point within the wafer along theline.